1. Field of the Invention
The present invention relates to recording heads and other types of heads used for recording apparatuses, and more particularly, to a recording head having a function for identifying the recording head, a recording apparatus having the recording head, a method for identifying the recording head, and a method for giving identification information to the recording head.
2. Description of the Related Art
The present invention can be applied to apparatuses such as a printer, a copying machine, a facsimile machine having a communication system, and a word processor having a printer all of which perform recording onto recording media, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, and ceramics. The present invention can also be applied to industrial recording apparatuses complexly combined with various processing apparatuses.
“Recording” in the present invention means not only giving a meaningful image such as a character or a figure to a recording medium, but also giving a meaningless image such as a pattern to a recording medium.
Conventional recording apparatuses are configured such that various recording heads and scanner heads can be replaceably mounted, to respond to various demands. As an example of such an apparatus, by preparing a scanner unit for optically reading the original in substantially the same shape as a recording head and using it instead of a printing head, a recording apparatus is used not only for recording but for reading the original. A recording apparatus can also be used for recording with different image quality by mounting another head having a different type of ink.
In another example, to compensate for dispersion in manufacturing recording heads, the best driving condition of a recording head is stored in the recording head when it is manufactured, and a recording apparatus automatically reads and identifies this driving condition to automatically set it.
In yet another example, to reduce cost by using common components in the heads corresponding to a plurality of recording apparatuses, the heads are manufactured in similar shapes. In this case, it is necessary to identify each head so as not to mount an erroneous head to each recording apparatus.
To respond to various demands such as those described above, it is demanded that a recording head be provided with means for identifying more types of recording heads.
Various methods have been used to satisfy such a demand. In a first method, a plurality of identification terminals are provided as terminals for electrically connecting a recording apparatus to a recording head, each of these terminals is grounded or connected to a power supply according to the type of the corresponding recording heads, and the recording head is identified by a low-level signal or a high-level signal. In this method, recording heads of the n-th power of 2 can be identified by providing “n” terminals.
In this method, however, many contacts are needed to identify many recording heads. This not only increases the cost of a recording head and a printing apparatus, but also reduces reliability as the number of contacts increases.
In a second method, electrically multi-level conditions are used in order to identify a plurality of states at one contact. In the simplest method, a resistor is provided for a recording head and the resistance thereof is read by a recording apparatus to identify the head.
In this method, although an identification resistor needs to be provided for a recording head, since it cannot be implemented just by the pattern of a contact, the cost increases. In addition, with dispersion of the contact resistance of a contact being taken into account, it is impossible to largely increase the types of recording heads which can be identified. Furthermore, a recording apparatus needs to have not only just a logic circuit but also an expensive circuit such as an A-D converter.
A third method uses serial data transfer. In this method, a circuit which implements serial transfer is provided for a head. A memory area for identification data is kept in the head and the data is transferred to the recording apparatus.
With this method, since any large amount of identification information can be transferred just by providing three terminals, one for the start pulse of serial transfer, a clock terminal, and a data terminal, in addition to usually required terminals such as the ground terminal and the power-supply terminal, a number of heads can be identified with this number of terminals. However, because these three terminals are positively required and a serial transfer circuit for identification information is also needed inside the apparatus, the cost thereof increases.
In any of the above methods, a number of terminals are required to give a large amount of identification information to the head, the cost increases, or reliability is not assured.